COMMON MUSK TURTLE (Sternotherus odoratus), (GRAY, 1825)
IDENTIFICATION: 2-4.5 inches (5-11.5 cm) The coloration of the carapace ranges from brown to almost black, gray or olive green. From a dorsal perspective it is oval. A series of dark spots are often present on the carapace scutes. The plastron varies in coloration from yellowish to brown. Adult specimens from some locations demonstrate a reduction in the amount of keratin covering the central portion of the plastron. Among these specimens a thin layer of flesh covers the bone as the fleshy areas between the plastral scutes increases with age. Most populations have an unhinged plastron. However, adult males in some populations (such as one in Comal County, Texas) demonstrate plastral kinesis at the anterior portion of the plastron. In one instance (among the Comal county population) the kinesis was exacerbated by a megacephalic head that essentially folded the anterior portion of the plastron inward whenever the head was withdrawn. Initially this specimen was thought to be missing the anterior portion of the plastron until its folded condition was realized. Plastral kinesis among musk turtles has been discussed before (Pritchard, *******) but this is the most extreme example known to date. Depending upon the age and locality of origin of the specimen the flesh can vary from tan with a suffusion of pink, light gray to nearly black and a pair of light colored stripes are present on the each side of the head. The lines start at the tip of the nose and extend over and under the eye onto the side of the head. Depending upon the age of the specimen the lines may be broken, faint, mottled or entirely faded.
BEHAVIOR AND ECOLOGY: This small turtle inhabits bodies of freshwater with soft bottoms and aquatic vegetation as well as areas with limestone in which they frequently seek refuge. Common musk turtles have been found in still to slow moving bodies of water as well as streams with swift currents. Populations from southern localities or from spring fed bodies of water may remain active the entire year. Female eastern musk turtles (Sternotherus odoratus) sometimes deposit their eggs directly onto leaf litter, but they will also dig a nest for their eggs, deposit them beneath leaf litter and under logs. Sometimes more than one female will use the same nesting site. Females usually lay between 2-5 elliptical brittle-shelled eggs per clutch. However, some females have produced as many as 9 eggs per clutch.
This species is primarily aquatic and not often found out of the water. Interestingly a fair number of deceased specimens can be encountered on roads near river and creek crossings. In some of these instances the road may be several feet above the water. Why the little turtles sometimes decide to make an arduous climb and cross a hazardous road instead of utilizing an unobstructed culvert in unknown. I have found individuals perched on culverts approximately 4 feet (1.5 meters) above the surface of the water that made a quick dive into the water after detecting my presence. Given the amount of time spent in the water, some specimens may bear a considerable amount of algae growth on their shells. Prey items are variable but aquatic snails, Asian mussels and insects constitute a majority of the diet.
These small turtles are susceptible to a wide range of predators including but not limited to predaceous diving beetles, (Family Dystictidae), large mouth bass (Micropterus sp.), bullfrogs (Lithobates catesbiana), kingsnakes (Lampropeltis getula), cottonmouths (Agkistrodon piscivorous), alligators (Alligator missippiensis), crows (Corvus sp.), bald eagles (Haliaeetus leucocephalus), hawks (Buteo sp.), skunks (Mephitis sp.) and racoons (Procyon lotor). Humans are responsible for more casualties than all of the other predators combined. Roadway mortality can be significant at some water crossings while boat propellers are responsible for an untold amount of turtle mortality. Whenever hooked by a fisherman this species is often killed. However, pollution and habitat loss in the form of drained wetlands poses the greatest threat.
LONGEVITY: The Philadelphia Zoo maintained a captive specimen for 54 years and 9 months.
GEOGRAPHIC DISTRIBUTION: This species occupies a geographic range that includes southern Ontario, Canada and New England westward to Wisconsin and southward to Florida and Texas. It is also the most northern ranging member of the family Kinosternidae.